| dc.description.abstract | Modern dairy farms strive to maximize milk price and control costs. This can be achieved by minimising the rate of disease, adequate management and future planning. This thesis examines the economic aspects of herd health management. In order to explore this topic I focused on the losses caused by mastitis, the importance of the dry cow period and the cost/benefit of the dry cow treatment. Mastitis can be both clinical and subclinical. Mastitis costs are caused by production losses, culling, visiting of veterinarians, drugs, discarded milk and labour. On many farms, subclinical is most economically important because of long-term effect of chronic infections on total milk yield. Mastitis pathogens can be separated into environmental and infective. The type of infection will depend on which type of pathogen involved. E. coli (environmental) will almost always cause a clinical infection. The total losses an infection will inflict, of course, depend on which stage of lactation it occurs. Earlier in the lactation the infection will have a longer effect and cause increased losses. The reduced production of milk is considered the largest loss contributing to mastitis. The SCC of milk is used to monitor udder health and milk quality. There is a relationship with SCC and disease, a quarter with over 250,000 SCC is considered to have subclinical mastitis. This reduces the profitability of the farm milk production but the calculation of the extent of economic loss is complex because of the many factors involved. There a relationship between SCC and milk quantity, this has been applied to linear score systems (LS) and can be used to calculate the overall losses caused by subclinical mastitis. The importance of the dry cow period in the dynamics of intramammary infection is well established. This paper shows the principal issues and attitudes concerning the dry cow period. The mammary gland is particularly susceptible to new intramammary infections during the early and late dry period, correlating with involution and colostrogenesis, respectively. A 60 day dry period ensures that on the day of calving the udder and the cow are in best physical condition for a healthy and productive future lactation. When not given sufficient time, this can have negative effects on consequent milking. It is essential to have adequate management of this crucial time, ensuring a stress free environment and appropriate fodder. The advised length is 60 days, but there are advantages for having shorter time periods in older cows. Some studies have indicated a shorter dry period may 34 lead to fewer metabolic problems after calving based on negative energy balance (NEB). There is a risk of early calving, and ending the dry period too early. This is a situation the farmer must prepare for, planning a 60 day dry period provides the farmer with a safety margin if complications occur. The cow should be prepared for the dry period in advance, with a BCS of 3.5. This can be worked on in the 2nd stage of lactation, utilizing the animals growing appetite and decreasing milk production. Antibiotic therapy at the end of lactation is the most effective and widely used mastitis control method for dry cows. The milk production after a long or short dry period differs. Reduction in milk production after a dry period shorter than 60 days is due to reduced functionality of the mammary parenchyma Best practice of dry cow treatment must include special attention to stress reduction, dry cow ration, cow comfort and the control of environmental pathogens. Treatment of the dry cow period is a costly and time consuming process. Steps must be taken to ensure the cow is getting the adequate treatment and in correct amounts. Factors affecting the risk include level of milk production at drying off, rapidity of involution, teat end condition, and level of contamination of teat. It is widely accepted that dry cow therapy is economically beneficial. Past studies on the different methods and scenarios used were compared and contrasted to see which was the most economically efficient and beneficial. In most countries blanket therapy is the standard way to treat drying off cows. The selective treatment is a modern alternative with concerns about antibiotic resistance. Decisions on cost-effective treatment should be made on individual cow level, depending on quarter infected state at drying off. The use of sealants, in general, is overall proven to be economically justified. However in other situations with low rates of new infection during the dry period, use of sealants may not be the most efficient choice and other strategies may need to be explored. Overall results show that dry cow antibiotic therapy remains a cost-effective measure compared with no treatment at all. The costeffectiveness of all strategies varies depending on the input parameters used. Better information on infection status at drying off, prevention of new infections and resulting cure is necessary in order to advise farmers properly. | en |
